Cannabis can induce mood change and sometimes psychotic symptoms in normal persons. In brain, the main active ingredient of cannabis acts via the cannabinoid CB1 receptor (CNR1) which is located on chromosome 6q14-15. Linkage studies have suggested the presence of a bipolar disorder susceptibility locus on chromosome 6q. In this population based association study, we tested the hypothesis that a microsatellite polymorphism in the promoter region of the CNR1 gene confers susceptibility to mood disorders and psychotic features. We genotyped the CNR1 gene is 154 mood disorder patients and 165 normal controls. The results showed that the triplet repeat polymorphism in the promoter region of the CNR1 gene was not likely to be involved in the pathogenesis or in the psychotic symptoms of mood disorders.